Method of aligning hardpoints in aeronautical structures

ABSTRACT

The present disclosure relates to a method of assembling hardpoints in aeronautical structures, and more specifically, the disclosed method allows knowing the relative deviation of the hardpoints and of the positioning elements of the hardpoints with respect to a laser beam emitted by a laser collimator fixed to an adjustable support which can be adjusted in at least two directions in space, and by using a correction algorithm, it is possible to know the displacement necessary for locating the positioning elements such that they are aligned with respect to the hardpoints, the positioning elements in turn being moved as a result of the movement of the driven linear tables in one or in several iterative steps, at which time the position thereof is fixed and they are ready for the rest of the hardpoints to be assembled.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a divisional of application Ser. No. 16/669,885,filed Oct. 31, 2019 and further claims priority to European PatentApplication n° 18382768.2 filed on Oct. 31, 2018, in English, the entirecontents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The method described in the invention follows the philosophy commonlyreferred to as adaptive tooling, which strives for a flexible toolingthat is suited to assembly circumstances and requirements foraeronautical structure.

More specifically, the present invention relates to a method forassembling hardpoints that need to be aligned with one another in anaeronautical structure in a very accurate manner, where hardpoints areunderstood to refer to those crucially important structural parts inwhich other structures are assembled and through which there passes theentire, or almost the entire structural load of the assembled element,for example the attachment fittings of the elevators or rudders,ailerons, spoilers, etc.

BACKGROUND OF THE INVENTION

The enormous increase in air traffic in recent years is well known,making air traffic a common means of transport for a large part of thepopulation. This has led to a considerable increase in the demand fornew aircraft both for offering new lines or services and for reinforcingexisting lines or services, as well as to the need to renovate fleets toreplace old and/or rather inefficient or non-cost effective aircraft.

The extremely high cost of manufacturing these aircraft is also verywell known, and for such manufacture, a quite significant part is usedin assembly operations, so for some time now there has been a need inthe aeronautical industry to reduce those expenses for the purpose ofimproving their competitiveness.

Furthermore, for the aeronautical industry this problem is compounded bythe requirement of high accuracy levels. For this reason, due to thecomplexity and the number of elements the end products have, theinaccuracies and deviations that build up during the processes formanufacturing the fundamental parts as they are gradually integratedinto sub-assemblies until forming the aircrafts become particularlyimportant.

These deviations often lead to the need to modify parts or change theassembly process in situ in a recurring manner to enable finishing theproduct, causing extremely high cost overruns and delays and renderingthe costs associated with those non-conformities present in aeronauticalstructure assembly operations the highest of all.

Some time ago, a first attempt to alleviate these problems consisted ofproposing improvements to the design, process, and tooling, in whichintrinsic inaccuracies of the processes were absorbed during assembly.

For example, in the case of jigs, the first systems were based onbuilding platforms made up of fixed devices which supported thecomponents and acted like auxiliary assembly aid elements, where eachportion of the structure of the aircraft had its own jig elements inwhat was known as a “dedicated tooling.” This system, however, requireda lot of time and a high cost both in terms of manufacture andmodification or rectification of the various elements of the jig or“master” tools as they were true pieces of craftsmanship.

After that, for the purpose of reducing costs the so-called “modulartooling” came about, which used standardized profiles to build thedifferent jigs, making it possible to recycle parts, and since theseparts were not welded, they could be adjusted and therefore providecertain flexibility when designing said jig. This system, which is basedon modularity in order to obtain the flexibility that is sought,basically consisted of creating a group of standard parts to whichdifferent portions are fixed by means of also standard nuts and bolts,and as a result of different grooves it also allowed fitting them indifferent positions. Furthermore, said parts were often recyclable,which allowed them to be reusable in subsequent assemblies.Nevertheless, although this technique improved the results of earliertechniques, its cost still left a lot of room for improvement.

More recently, with the rise of three-dimensional laser measuringequipment, such as that commonly referred to as laser trackers, mastertools gave way to the in situ calibration of the jig with accuracies ofup to 10 microns. Nevertheless, these systems also suffer from thedrawback of lacking any flexibility whatsoever, given that in order tochange the positions of the devices, a laser tracker is required forgetting them ready with accuracy, however this equipment is tooexpensive and the process for getting them ready takes too long to do ineach manufacturing process.

Also with the rise of guided robots (vision-guided, laser-guided, etc.),flexible manufacturing processes can be carried out today with accuracy.Nevertheless, the cost of paying off the robot is once again asignificant economic barrier, particularly in the case of the aerospaceindustry where the manufacturing output is lower compared to otherindustries, such as the automotive industry, for example.

So for the purpose of overcoming the aforementioned drawbacks, there areessentially two techniques today that employ a different philosophy butpursue the same objective, i.e., making assembly processes as flexibleas possible such that such processes adjust or adapt to the changingcircumstances of production without affecting product quality and at acompetitive cost in terms of both material and time.

One of these techniques is referred to as a jigless technique, i.e., onewithout a jig, which pursues, as its own name indicates, the completeelimination or the most complete elimination possible of the jig.

The main advantage of this technique is the considerable savings inmaterial costs, and also the savings in time. Furthermore, extremelyhigh levels of accuracy can be achieved in the case of applying lasertechniques such as the technique described in patent documentEP18382127, belonging to the present applicant.

Said technique, however, also suffers from the drawback that, since itis not equipped with a jig, the aeronautical structure is assembled onitself, which sometimes hinders accuracy due to the fact that theabsence of rigidity does not allow performing the final tasks forattaching the different elements, such as drilling, riveting, etc., withthe required accuracy. In other words, although the method allows forvery good adaptability to the product and although very high accuracy isachieved during the first assembly phase, said accuracy may bediminished in the final operations.

The other alternative technique with respect to not using a jig or thejigless technique which achieves said adaptability despite using a jigis referred to as adaptive tooling, which pursues the dual purpose ofabsorbing deviations of the assemblies and adjusting to circumstancesfor the purpose of lowering costs, but without this affecting finalproduct accuracy/quality.

SUMMARY

The method of the present invention belongs to those techniques referredto as adaptive tooling techniques, but it solves the problems of theprior art given that the position of the different assembly tools orelements making up the jig theoretically is not predetermined, butrather is determined by the position of other parts already previouslyassembled during the assembly process.

Furthermore, given that a jig is used, the method of the presentinvention has the advantage with respect to the technique in which a jibis not used, referred to as a jigless technique, in that it has rigidpoints that allow performing the last drilling and/or rivetingoperations of the assembly with maximum accuracy.

In other words, the disclosed method makes the jig used during theassembly adaptive, which translates into a larger number of compliantproducts, and therefore into cost savings. Specifically, given that thedisclosed method is based on making the jig adaptive, i.e., flexiblewhen being positioned, compliance of the final assembly is achieved insome cases in which the elements making up said assembly could beconsidered non-compliant as they are outside certain tolerance limits ifthey were assembled by means of other assembly techniques or methodsthat do not allow said flexibility.

The invention now described generally consists of a method based on theuse of a laser positioning device for marking the position in which saidassembly tools or elements making up the jig must be placed, eitherautomatically or manually, in order for them to be aligned. Therefore,said laser positioning devices allow positioning in an accurate andflexible manner the hardpoints of an aerostructure aligned with otherparts of the assembly that have previously been assembled in thestructure.

In other words, the disclosed method is based on the use of a lasersystem that allows aligning different tooling devices in an accuratemanner for the subsequent attachment thereof to the rest of thestructure to be assembled.

The disclosed method is, therefore, suitable for carrying out thealignment and assembly of mobile aeronautical structures, i.e.,structures that interact with the air and allow changing said form ofinteraction, such as control surfaces, for example: ailerons, elevatorsor rudders, or any other structure requiring the alignment of itshardpoints with a very narrow tolerance.

On the other hand, the disclosed method needs an auxiliary structure asa support which allows positioning the different parts or sub-assembliesmaking up the structure to be assembled for the correct assemblythereof, i.e., the assembly tool for the structure at hand whichcomprises:

-   -   positioning devices or positioning elements for the hardpoints,        where said positioning devices allow restricting one or several        degrees of freedom of a part or sub-assembly of parts, such that        the proper positioning thereof with respect to the others is        assured; and    -   a structure for supporting the structure to be assembled and the        positioning devices themselves in a sufficiently rigid manner.

And additionally the following elements:

-   -   a collimator equipment or a laser beam emitter;    -   an adjustable support for the laser collimator;    -   at least one coaxiality sensor capable of detecting the        incidence of the laser beam on its surface and knowing its        position with respect to a reference system in the device        itself; i.e., a sensor which allows measuring the relative        deviation of the laser beam emitted by the collimator with        respect to the sensor itself;    -   2-axis driven linear tables which consist of supports with one        or more linear guides or tracks which allow displacing one        element with respect to another, that is, they specifically        allow displacement in two perpendicular directions, and        therefore on one plane;    -   mechanical actuators or devices the function of which is to        provide force for moving the driven linear tables and which can        be operated by hand or, for example, by an electric motor; and    -   a computer system connected to both the coaxiality sensors and        the actuators so as to interact with them and, through an        interface, allow the user to perform the drive and direct the        method and obtain information useful for the development of said        method.

More specifically, the laser collimator is assembled on a support and isadjusted such that the beam it emits goes through the holes of the fixedhardpoints previously installed in the structure. Therefore, the drivenlinear tables are driven precisely because the actuators are connectedthereto. These driven linear tables are coupled to the positioningelements, thereby obtaining control over the movement thereof. Finally,the coaxiality sensors are installed in the fixed hardpoints and in thepositioning elements such that the laser beam strikes them and thedeviation of said laser beam with respect to the coaxiality sensors, andvice versa, can thereby be known.

Therefore, as a result of the preceding configuration the relativedeviation of the fixed hardpoints and of the positioning elements withrespect to the laser beam is known, and by using a correction algorithm,it is possible to know the displacement necessary for locating thepositioning elements such that they are aligned with respect to thefixed hardpoints, said positioning elements being moved in turn as aresult of the movement of the driven linear tables. Specifically, bymeans of the movement of the driven linear tables, in one or in severaliterative steps, the positioning elements are located until beingaligned with the fixed hardpoints, at which time the position thereof isfixed and they are ready for the assembly of the rest of the hardpoints.

As described above, the method of the invention thereby allows anassembly tool to adapt its position to the product or structure to beassembled, improving the accuracy of the alignment of the hardpointsthat is achieved with a conventional tool and without such high costs asthose involved with a guided robot.

Having said the foregoing, the steps comprised in the disclosed methodare described for a particular product, for example one of thoseproducts mentioned above, once it is fixed on the auxiliary orsupporting structure and is equipped with two hardpoints assembled in apreceding step with another assembly tool, and said steps are thefollowing:

-   -   1) INSTALLING AND ADJUSTING THE LASER COLLIMATOR. In this step,        the laser collimator is assembled in its support and adjusted so        that it goes through the through holes with which the already        installed hardpoints and the positioning elements are equipped.        It should be pointed out that it is not necessary for the laser        beam to go through the exact center of said holes, since it is        sufficient for it to be within the reading range of the        coaxiality sensor, which is usually several millimeters.    -   2) COUPLING THE COAXIALITY SENSOR OR SENSORS. The sensor is        coupled (if a sequential measurement is taken one by one) or the        coaxiality sensors are coupled (if the measurement is        simultaneous) to the hole of the already installed hardpoints        and of the positioning elements.    -   3) MEASURING HARDPOINTS AND POSITIONING ELEMENTS. The laser beam        strikes the coaxiality sensor or sensors located in the        hardpoints and in the positioning elements, showing their        deviation with respect to the local reference system of said        coaxiality sensors.    -   4) CALCULATING THE DISPLACEMENT OF THE POSITIONING ELEMENTS.        Once the deviations with respect to the laser beam are known,        the correction algorithm is applied to calculate the necessary        displacements to which the positioning elements are to be        subjected for proper alignment of the hardpoints.    -   5) MOVING THE POSITIONING ELEMENTS. The driven linear tables        perform horizontal and vertical displacements equivalent to        those displacements calculated in the preceding paragraph,        resulting in the positioning element being positioned such that        it is aligned.    -   6) CHECKING THE POSITIONING ELEMENTS. A new reading of the new        position of the positioning elements according to paragraph 3        above is taken, and in the event of being considered unsuitable,        a new calculation of the displacement of the positioning        elements is performed by repeating steps 4 and 5.    -   7) FIXING THE POSITIONING ELEMENTS. Once it is checked that the        alignment between fixed hardpoints and positioning elements is        good enough, the position of the actuators and therefore of the        positioning elements is locked.    -   8) ASSEMBLING THE REST OF THE HARDPOINTS. After that point, the        coaxiality sensor or sensors are disassembled and the rest of        the points are assembled as if it were a conventional jig, i.e.,        by means of the known operations of drilling, sealing, riveting,        etc., and additionally    -   9) VERIFYING HARDPOINTS. The present invention also allows        verifying the final alignment of the hardpoints with accuracy,        for which purpose the coaxiality sensor or sensors must simply        be coupled to the hardpoints with different adapter sockets and        the calculation must be performed in the same way as with the        positioning elements.

The present summary is provided only by way of example, and notlimitation. Other aspects of the present invention will be appreciatedin view of the entirety of the present disclosure, including the entiretext, claims and accompanying figures.

DESCRIPTION OF THE DRAWINGS

To complement the description that is being made and for the purpose ofhelping to better understand the features of the invention, a set ofdrawings is attached to the present specification as an integral partthereof, in which the following is depicted in an illustrative andnon-limiting manner:

FIG. 1 schematically shows a structure of the control surface type ofthe state of the art which could be an aileron, a rudder, or anelevator.

FIG. 2 schematically shows an assembly tool for assembling a structureof the control surface type shown in FIG. 1 .

FIG. 3 shows a schematic perspective view of the main elements involvedin the application of the method of assembly of the invention.

FIG. 4 shows a detail view of the support for the laser collimator forcarrying out the method of the invention.

FIG. 5 shows several detail views of how the coaxiality sensor iscoupled both to the hole of the hardpoints and to the hole of thepositioning elements.

FIG. 6 shows a perspective view of how the laser beam strikes thecoaxiality sensor and the schematic depiction of the deviation of saidbeam on the plane defined by said sensor.

FIG. 7 shows a perspective view of a horizontal driven table and avertical driven table, and of the movement said tables impart on theirpositioning element.

FIG. 8 shows a schematic perspective view of the measurement of thefinal position of the new hardpoints which have been assembled with thepositioning elements (not depicted) so that they are aligned with theinitial hardpoints.

FIG. 9 shows various schematic perspective views of the steps to betaken according to the method of the invention for the case of using asingle opaque coaxiality sensor in a sequential manner.

FIG. 10 shows a schematic drawing of the mathematical demonstration ofthe calculation of displacements for the example in which there arealready installed hardpoints A and B and a hardpoint C is to be aligned.

FIG. 11 schematically shows a detail of the incidence of the laser onthe sensor of hardpoint B for the case of FIG. 10 above.

FIG. 12 schematically shows a detail of the incidence of the laser inthe sensor located in positioning element “C” when the latter is alignedwith hardpoints “A” and “B” of FIGS. 10 and 11 above.

FIG. 13 shows several schematic views of the geometric calculation ofthe displacement vector.

While the above-identified figures set forth one or more embodiments ofthe present invention, other embodiments are also contemplated, as notedin the discussion. In all cases, this disclosure presents the inventionby way of representation and not limitation. It should be understoodthat numerous other modifications and embodiments can be devised bythose skilled in the art, which fall within the scope and spirit of theprinciples of the invention. The figures may not be drawn to scale, andapplications and embodiments of the present invention may includefeatures, steps and/or components not specifically shown in thedrawings.

DESCRIPTION OF PREFERRED EMBODIMENT(S) OF THE INVENTION

In view of the mentioned drawings, and according to the numbering used,the method of assembling hardpoints in mobile aeronautical structures ofthe invention can be seen therein.

More specifically, a representative drawing of the aforementionedalready known structures, which have a specific number of hardpoints (1)having their holes aligned with a very narrow tolerance as a requirementcan be seen in FIG. 1 . Specifically, said FIG. 1 shows a longeron (2),ribs (3), skins (4), and the mentioned fittings or hardpoints (1), amongothers.

On the other hand, as can be seen in FIG. 2 , the method of theinvention needs a supporting structure which allows positioning thedifferent parts or sub-assemblies making up the structure to beassembled for the correct assembly thereof, i.e., the assembly tool ofthe structure at hand which comprises:

-   -   positioning devices or positioning elements (5) for the        hardpoints, where said positioning elements (5) allow        restricting one or several degrees of freedom of a part or        sub-assembly of parts such that the proper positioning thereof        with respect to the others is assured;    -   an auxiliary structure (6) for supporting the assembly and the        positioning elements (5) themselves in a sufficiently rigid        manner.

And additionally the following elements:

-   -   laser collimator equipment (7) or a laser beam emitter,    -   an adjustable support (8) for the laser collimator (7),    -   at least one coaxiality sensor (9, 9′) capable of detecting the        incidence of the laser beam (7′) on its surface and knowing its        position with respect to a reference system in the device        itself, i.e., a sensor which allows measuring the relative        deviation of the laser beam emitted by the laser collimator (7)        with respect to the coaxiality sensor (9, 9′) itself.    -   These coaxiality sensors (9, 9′) could be of two types according        to two possible alternative embodiments of the invention.        Specifically, one of such alternative embodiments will be one in        which the coaxiality sensors (9) are translucent, i.e., they        allow the laser beam (7′) to pass through, in which case        arranging sensors in all the holes of interest would be        sufficient to obtain the measurements of each one of them        simultaneously. The other alternative embodiment will be one in        which the coaxiality sensors (9′) are opaque, and in this case        it is necessary to perform several steps of the method in a        sequential manner since not all the measurements can be taken at        the same time.    -   2-axis adjustable driven linear tables (10) which consist of        supports with one or more linear guides or tracks which allow        displacing an element with respect to another, that is, they        specifically allow displacement in two perpendicular directions,        and therefore on one plane.    -   mechanical actuators or devices (not depicted) the function of        which is to provide force for moving the driven linear tables        and which can be operated by hand or, for example, by an        electric motor; and    -   a computer system connected to both the coaxiality sensors and        the actuators so as to interact with them and, through an        interface, allow the user to perform the drive and direct the        method and obtain information useful for the development of said        method.

More specifically, as can particularly be seen in FIG. 3 , the lasercollimator (7) is assembled on an adjustable support (8) such that theemitted beam (7′) goes through the holes of the hardpoints (1)previously installed in the structure. The actuators are connected tothe driven linear tables (10) to provide said drive. These driven lineartables (10) are coupled to the positioning elements (5), therebyobtaining control over the movement thereof. Finally, the coaxialitysensors (9) are installed in the hardpoints (1) and in the positioningelements (5) such that the laser beam (7′) strikes them and thedeviation of said laser beam (7′) with respect to the coaxiality sensors(9), and vice versa, can thereby be known.

Therefore, as a result of the preceding configuration the relativedeviation of the hardpoints (1) and of the positioning elements (5) withrespect to the laser beam (7′) is known, and by using a correctionalgorithm, it is possible to know the displacement necessary forlocating the positioning elements (5) such that they are aligned withrespect to the hardpoints (1), said positioning elements (5) in turnbeing moved as a result of the movement of the driven linear tables(10), which comprise at least two driven portions, a horizontal drivenportion (10′) and a vertical driven portion (10″). Specifically, bymeans of the movement of the driven linear tables (10), in one or inseveral iterative steps, the positioning elements (5) are located untilbeing aligned with the hardpoints (1), at which time the positionthereof is fixed and they are ready for the rest of the hardpoints (1)to be assembled.

Therefore, according to a preferred embodiment, in order to carry outthe assembly of a given product or structure once it is fixed on theauxiliary structure or support and is already equipped with twohardpoints assembled thereon, the steps comprised in the method of theinvention according to the case in which translucent coaxiality sensors(9) are used are as follows:

-   -   1) INSTALLING AND ADJUSTING THE LASER COLLIMATOR (7). As can be        seen in FIG. 4 , in this step the laser collimator (7) is        assembled in its adjustable support (8) and adjusted so that the        laser beam (7′) goes through the through holes with which the        already installed hardpoints (1) and positioning elements (5)        are equipped. It must be pointed out that it is not necessary        for the laser beam (7′) to go through the exact center of said        holes, since it is sufficient for it to be within the reading        range of the coaxiality sensor (9), which is usually several        millimeters. As can be seen in said drawing, the adjustable        support (8) is equipped with an adjustment such that it is        possible to move it in at least two directions in space, for        example horizontal and vertical, as well as to turn it        horizontally and vertically for the purpose of orienting the        laser beam (7′) towards the coaxiality sensors (9).    -   2) COUPLING THE COAXIALITY SENSORS (9). As can be seen in FIG. 5        , the coaxiality sensors are coupled in the hole of the already        installed hardpoints and of the positioning elements (5). More        specifically, said drawing shows a detail of the coaxiality        sensor (9) and how it is coupled by means of a built-in cylinder        (12) and adapter sockets (11) to the hole of the hardpoints (1)        and of the positioning elements (5).    -   3) MEASURING HARDPOINTS (1) AND POSITIONING ELEMENTS (5). As can        be seen in FIG. 6 , the laser beam (7′) strikes the coaxiality        sensors (9) located in the hardpoints (1) and in the positioning        elements (5), showing their deviation (13) with respect to the        local reference system of said coaxiality sensors (9).    -   4) CALCULATING THE DISPLACEMENT OF THE POSITIONING ELEMENTS (5).        Once the deviations with respect to the laser beam (7′) are        known, the correction algorithm described in detail below is        applied to calculate the necessary displacements to which the        positioning elements (5) are to be subjected for proper        alignment of the hardpoints (1).    -   5) MOVING THE POSITIONING ELEMENTS (5). As shown in FIG. 7 , the        driven linear tables (10), and more specifically their        horizontal driven portion (10′) and their vertical driven        portion (10″), perform displacements equivalent to those        calculated in the preceding paragraph, resulting in the        positioning element (5) being aligned.    -   6) CHECKING THE POSITIONING ELEMENTS (5). A new reading of the        new position of the positioning elements (5) according to        paragraph 3 above is taken, and in the event of being considered        unsuitable, a new calculation of the displacement of the        positioning elements (5) is performed by repeating steps 4 and        5.    -   7) FIXING THE POSITIONING ELEMENTS (5). Once it is checked that        the alignment between hardpoints (1) and positioning elements        (5) is good enough according to the established quality        criterion, the position of the actuators and therefore of the        positioning elements (5) is locked.    -   8) ASSEMBLING THE REST OF THE HARDPOINTS (1). After that time,        the coaxiality sensors (9) are disassembled and the rest of the        hardpoints (1) are assembled to then also apply to same steps 2        to 7 of the described method; and finally, in an optional        manner,    -   9) VERIFYING HARDPOINTS (1). As can be seen in FIG. 8 , the        present invention also allows verifying the final alignment of        the hardpoints (1) with accuracy, for which purpose the        coaxiality sensors (9) must simply be coupled to the hardpoints        (1) with different adapter sockets (11) and the calculation must        be performed in the same way as with the positioning elements        (5). In other words, said drawing shows a scheme for measuring        the final position of the new hardpoints (1) which have been        assembled with the positioning elements (5) (not depicted) so        that they are aligned with the initial hardpoints (1).

Finally, FIG. 9 shows an alternative embodiment of the method of theinvention for the case in which a single opaque coaxiality sensor (9′)is used in a sequential manner. Therefore, as can be seen, first theposition of a hardpoint (1) located, for example, at one of the ends, ismeasured, and then the position of another hardpoint (1′) located, forexample, at the other end, is measured. After having established theposition of both hardpoints (1, 1′) with respect to the laser beam (7′),each of the positioning elements (5) is adjusted in a sequential manner.

Therefore, according to another possible embodiment, in order to carryout the assembly of a given product or structure once it is fixed on theauxiliary structure or support and is already equipped with twohardpoints assembled thereon, the steps comprised in the method of theinvention according to the case in which opaque coaxiality sensors (9′)are used are as follows:

-   -   a) Installing on the auxiliary structure (2) a laser collimator        (7) on an adjustable support (8) which can be adjusted in at        least two directions in space for the purpose of orienting the        laser beam (7′) so that it passes through a number of through        holes with which two already installed hardpoints (1) are        equipped;    -   b) Coupling a coaxiality sensor (9′) in the through hole with        which the first of the two already installed hardpoints (1) is        equipped;    -   c) Measuring the deviation of the point where the laser beam        (7′) strikes the coaxiality sensor (9′) located in the first        hardpoint (1) with respect to a local reference system of said        coaxiality sensor (9′);    -   d) Coupling the coaxiality sensor (9′) in the through hole with        which the second of the two already installed hardpoints (1) is        equipped;    -   e) Measuring the deviation of the point where the laser beam        (7′) strikes the coaxiality sensor (9′) located in the second        hardpoint (1) with respect to a local reference system of said        coaxiality sensor (9′);    -   f) Coupling the coaxiality sensor (9′) in the through hole with        which one of the positioning elements (5) is equipped;    -   g) Measuring the deviation of the point where the laser beam        (7′) strikes the positioning element (5) by obtaining its        deviation (13) with respect to the local reference system of the        coaxiality sensor (9, 9′);    -   h) Once the deviations with respect to the laser beam (7′)        obtained in the preceding step are known, applying a correction        algorithm to calculate the necessary displacements to which the        positioning element (5) is to be subjected for proper alignment        of the hardpoint (1) associated with it;    -   i) Shifting the positioning element (5) according to the value        obtained in the preceding step, resulting in the positioning        element (5) being aligned;    -   j) Taking a new reading of the position of the positioning        element (5) according to paragraph g) above, and in the event of        being considered unsuitable according to a previously        established quality criterion, performing another calculation of        the displacement of the positioning elements (5) by repeating        steps h) and i);    -   k) Once it has been found that the alignment between the already        installed hardpoints (1) and the positioning element (5) is        sufficient according to the established quality criterion,        locking the position of said positioning element (5);    -   l) Removing the coaxiality sensor (9′) from the already aligned        positioning element and repeating steps f) to k) for the rest of        the positioning elements (5);    -   m) Assembling the rest of the hardpoints (1) to then also        sequentially apply to same the preceding steps b) to l) of the        described method; and in an optional manner,    -   n) Verifying the final alignment of all the already installed        hardpoints (1) by coupling the coaxiality sensor (9′) in a        sequential manner directly to the hardpoints (1) and performing        the calculation of the deviation in the same way as with the        positioning elements (5).

Below, as indicated in the steps of the methods described above, FIGS.10 to 13 describe an example of a correction algorithm to calculate thenecessary displacements to which the positioning elements (5) are to besubjected for proper alignment of the hardpoints (1).

Therefore, FIG. 10 shows hardpoints A, B, and C, where A and B arepreviously installed and C is the hardpoint to be aligned. Points a_(R),b_(R), and c_(R), which are the centers of the sensors coupled to thementioned hardpoints, and also points a_(L), b_(L), and c_(L), which arethe points where the laser beam strikes each sensor, are likewise shown.Finally, the global reference system {A, X, Y, Z} that is used is shown.

More specifically, there are two previously installed hardpoints (1) “A”and “B”, with respective installed sensors the central points of whichare “a_(R)” and “b_(R)”; a positioning element (5) of the hardpoint C tobe installed such that it is aligned with “A” and “B” with an installedsensor the central point of which is “c_(R)”; a fictitious line “R”defined by points “a_(R)” and “b_(R)”; a laser beam “L” coming from thelaser collimator (7) which strikes the sensors of the three hardpointsat points “a_(L)”, “b_(L),” and “c_(L)”; a global reference system S={A,X, Y, Z} the origin of which is “A”, the axis “Z” of which is parallelto the fictitious line “R” and the axes “X” and “Y” of which areparallel to the local axes of each sensor “x” and “y”, respectively.

The distances in direction “Z” are very large compared to the deviationsin “X” and “Y”, so the working hypothesis is that the angle between line“R” and line “L” is very small. This means that small variations indirection “Z” will not cause significant variations in “X” and in “Y”.

On the other hand, FIG. 11 shows the detail of the incidence of thelaser on the sensor of hardpoint B, which is valid for any otherhardpoint. It is shown how the coordinates of the points of incidence ofthe laser “a_(L)”, “b_(L),” and “c_(L)” are obtained from the readingsof the sensors and theoretical “Z”.

More specifically, each of the sensors coupled to the hardpoints willprovide a reading of the coordinates of the point of incidence of thelaser in the local reference system of each sensor Δx_(l) and Δy_(l)which coincide, under the hypotheses considered, with coordinates “X”and “Y” in the global reference system. Coordinate “Z” is not preciselyknown such that under the hypotheses considered above, theoretical “Z”can take “z_(t)” without causing significant variations in “x” or in“y”. The coordinates of the points of incidence of the laser on each ofthe sensors “a_(L)”, “b_(L),” “c_(L)”, in the reference system “S” arethereby known. They are known specifically from the expression:a _(L)=(Δx _(l) ^(a) ,Δy _(l) ^(a) ,z _(t) ^(a))b _(L)=(Δx _(l) ^(b) ,Δy _(l) ^(b) ,z _(b) ^(t))c _(L)=(Δx _(l) ^(c) ,Δy _(l) ^(c) ,z _(t) ^(c))where Δx_(l) ^(a) and Δy_(l) ^(a) are the deviations measured by thesensor coupled to hardpoint A and z_(t) ^(a) is the theoreticalcoordinate z of hardpoint A; where Δx_(l) ^(b) and Δy_(l) ^(b) are thedeviations measured by the sensor coupled to hardpoint B and z_(t) ^(b)is the theoretical coordinate z of hardpoint B; and where Δx_(l) ^(c)and Δy_(l) ^(c) are the deviations measured by the sensor coupled tohardpoint C and z_(t) ^(c) is the theoretical coordinate z of hardpointC.

Therefore, by using the coordinates of the points of incidence of thelaser “a_(L)”, “b_(L),” line “L” is calculated using the so-calledequations of a line, which are equations which mathematically representall the points making up a line, in this case the points making up thelaser beam. In that sense:

$L = \begin{Bmatrix}{X = {{mZ} + n}} \\{Y = {{m^{\prime}Z} + {n'}}}\end{Bmatrix}$${m = \frac{{\Delta x_{l}^{a}} - {\Delta x_{l}^{b}}}{z_{t}^{a} - z_{t}^{b}}};{n = {{{\Delta x_{l}^{a}} - {\frac{{\Delta x_{l}^{a}} - {\Delta x_{l}^{b}}}{z_{t}^{a} - z_{t}^{b}}z_{t}^{a}}} = {{\Delta x_{l}^{b}} - {\frac{{\Delta x_{l}^{a}} - {\Delta x_{l}^{b}}}{z_{t}^{a} - z_{t}^{b}}z_{t}^{b}}}}}$${m^{\prime} = \frac{{\Delta y_{l}^{a}} - {\Delta y_{l}^{b}}}{z_{t}^{a} - z_{t}^{b}}};{n^{\prime} = {{{\Delta y_{l}^{a}} - {\frac{{\Delta y_{l}^{a}} - {\Delta y_{l}^{b}}}{z_{t}^{a} - z_{t}^{b}}z_{t}^{a}}} = {{\Delta y_{l}^{b}} - {\frac{{\Delta y_{l}^{a}} - {\Delta y_{l}^{b}}}{z_{t}^{a} - z_{t}^{b}}z_{t}^{b}}}}}$where m and m′ are the slopes (inclination) of line L with respect toplanes YZ and XZ, respectively;where n and n′ are coordinates “x” and “y”, respectively, of the pointof intersection of line L with plane XY; andwhere X, Y, and Z are the coordinates of any one point belonging to lineL.

Therefore, as can be seen in FIG. 12 , which shows a sketch of the laserbeam striking the sensor of positioning element “C” when it is alignedwith hardpoints “A” and “B”, with the equation of the line of the laserbeam “L” being known, coordinates “X” and “Y” of point “c_(o)” arecalculated by substituting therein theoretical coordinate “Z” ofhardpoint “C”. In that sense:c _(o)=(x _(o) ^(c) ,y _(o) ^(c) ,z _(o) ^(c))x _(o) ^(c) =m·z _(t) ^(c) +ny _(o) ^(c) =m′·z _(t) ^(c) +n′z _(o) ^(c) =z _(t) ^(c)where z_(t) ^(c) is theoretical coordinate z of hardpoint C.

And where point “c_(o)” is the point of the sensor on which the lasermust strike when the positioning element of hardpoint “C” is alignedwith hardpoints “A” and “B”, so it is referred to as the target point.It should be observed that the laser beam does not have to be aimed atthe center of the sensor of positioning element “C”; this only occurswhen the laser beam has been positioned such that it also goes throughthe exact center of the sensors of hardpoints “A” and “B”.

Finally, as can be seen, FIG. 13 shows a sketch of the displacementvector which gets the beam to successfully go from striking “c_(L)” to“c_(o)”. Specifically, FIG. 13.1 geometrically demonstrates how thedisplacement vector is calculated; FIG. 13.2 shows the sensor ofpositioning element “C” in the initial position which is displaced tothe target position of FIG. 13.3 , i.e., the position in whichpositioning element “C” is aligned with hardpoints “A” and “B”.

In other words, once the initial point of incidence of laser “c_(L)” isknown, displacement vector “D_(C)” which the positioning element must bemoved for the point of incidence to be “c_(o)” is calculated. In thatsense:D _(C) =c _(L) −c _(o)=(x _(D) ^(c) ,y _(D) ^(c))x _(D) ^(c) =Δx _(L) ^(c) −x _(o) ^(c)y _(D) ^(c) =Δy _(L) ^(c) −y _(o) ^(c)

where x_(D) ^(c) is the theoretical displacement that must be applied topositioning element C to align it with A and B by means of the mentionedhorizontal driven portion (10′) of the driven linear tables (10); and

where y_(D) ^(c) is the theoretical displacement that must be applied topositioning element C to align it with A and B by means of the mentionedvertical driven portion (10″) of the driven linear tables (10).

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

The invention claimed is:
 1. A method involving placement of anaeronautical structure which already has two hardpoints installed on anauxiliary structure, where said auxiliary structure in turn includes aset of positioning elements which allow varying their position accordingto at least one degree of freedom, the method comprising the steps of:a) installing on the auxiliary structure a laser collimator on anadjustable support which can be adjusted in at least two directions inspace for orienting a laser beam from the laser collimator so that thelaser beam passes through a number of through holes with which the twoalready installed hardpoints are equipped; b) coupling an opaquecoaxiality sensor in a first of the through holes with which the firstof the two already installed hardpoints is equipped; c) measuring adeviation of a point where the laser beam strikes the coaxiality sensorlocated in the first of the two already installed hardpoints withrespect to a local reference system of said coaxiality sensor; d)coupling the coaxiality sensor in a second of the through holes withwhich the second of the two already installed hardpoints is equipped; e)measuring a deviation of the point where the laser beam strikes thecoaxiality sensor located in the second of the two already installedhardpoints with respect to a local reference system of said coaxialitysensor; f) coupling the coaxiality sensor in one of the through holeswith which one of the set of positioning elements is equipped; g)measuring a deviation of the point where the laser beam strikes acorresponding positioning element of the set of positioning elements byobtaining its deviation with respect to the local reference system ofthe coaxiality sensor; h) once the deviations with respect to the laserbeam obtained in the preceding step are known, applying a correctionalgorithm to calculate necessary displacements to which the positioningelement is to be subjected for proper alignment of the hardpointassociated with the corresponding positioning element; i) shifting thepositioning element according to a displacement value obtained in thepreceding step, resulting in the positioning element being aligned; j)taking a new reading of the position of the corresponding positioningelement according to step g) above, and in the event of being consideredunsuitable according to a previously established quality criterion,performing another calculation of the displacement of the set ofpositioning elements by repeating steps h) and i); k) once it has beenfound that the alignment between the two already installed hardpointsand the corresponding positioning element is sufficient according to thepreviously established quality criterion, locking the position of saidcorresponding positioning element; l) removing the coaxiality sensorfrom the already aligned positioning element and repeating steps f) tok) for the rest of the set of positioning elements; and m) assemblingthe rest of the hardpoints to which the preceding steps b) to l) of themethod are then performed.
 2. The method according to claim 1, andfurther comprising the additional step of: n) verifying a finalalignment of all the already installed hardpoints by coupling the opaquecoaxiality sensor in a sequential manner directly to the hardpoints andperforming the calculation of the deviation in the same way as with theset of positioning elements.
 3. The method according to claim 1, whereinthe correction algorithm to calculate the necessary displacements towhich the positioning elements are to be subjected for proper alignmentof the hardpoints comprises: calculating a line R going through centralpoints of the installed coaxiality sensor; calculating a line L goingthrough points of incidence of the laser beam on the coaxiality sensor;using both lines R and L, calculating coordinates of a target point ofthe coaxiality sensor where the laser beam must strike when thepositioning element of the hardpoint to be aligned is aligned with thetwo already installed hardpoints; and calculating a displacement vectorthat the positioning element must be moved so that the point ofincidence is the target point.
 4. The method according to claim 1,wherein the displacement of the set of positioning elements according tostep e) is performed using driven linear tables comprising a horizontaldriven portion and a vertical driven portion.